Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 653)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 629
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Configuring BGP VPNs on a PE
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Brocade(config-bgp-ipv4u-vrf)# neighbor 10.33.36.2 allowas-in 3
Syntax: [no] neighbor IPaddress allowas-in asn_limit
The IPaddress is the IP address of the neighbor CE device from which the PE device can accept
routes that have the same AS number.
The asn_limit value prevents loops by limiting the number of occurrences that the PEs AS number
can be accepted in routes that are received from the specified device.
Setting up LSPs per VRF
IBGP is used between PEs to determine routes that are available between VRFs. These routes are
linked to a Label Switched Path (LSP) that has been defined separately either as a static path or
using LDP or RSVP. The LSP is used to tunnel through the MPLS domain to the destination PE.
Under most circumstances, the default route between two PEs is chosen by IBGP between the VRFs
with the PEs loopback address as the next hop. When there is a single loopback on the PE, the
same LSP tunnel is the only path used between any VRF defined on a PE and VRFs on other
specified PEs.
More than one LSP can be configured between PEs however, where each LSP is associated with a
different Loopback address on the PE. In this case, any loopback address on a PE can be assigned
as the nexthop address for a specific or multiple VRFs. This allows the user to assign some VRFs on
a PE to one LSP and other VRFs to a different LSP. Through this method, traffic from different VRFs
can be assigned to LSPs that provide different qualities of service. This feature can also be
employed to provide for load-balancing across the MPLS domain.
To configure a PE device to use different LSPs, a BGP next hop must be configured for a VRF as the
following example illustrates.
Brocade(config)# vrf blue
Brocade(config-vrf-blue)# bgp next-hop loopback 2
Brocade(config-vrf-blue)# exit-vrf
Brocade(config)#
Syntax: [no] bgp next-hop loopback-interface
The loopback-interface variable is the number of the loopback interface that the user is assigning
to the VRF as a BGP next hop. The loopback address becomes the defined VRF's nexthop for its
VPNv4 routes that are sourced by this device only when:
• The loopback interface exists and has an IP address set.
• The loopback interface has an IP a subnet mask of /32
• The loopback interface is in the default VRF.
When these conditions are not met, the default nexthop is used.
For a detailed example of this feature refer to “Setting an LSP for each VRF on a PE” on page 732.